English
employs some unscientific, yet interesting, language to describe events
occurring in everyday life. For example, storks fly through the sky to deliver babies, and
people catch a
bug that makes them sick. These expressions came about as early
humans tried to explain the world around them. Although modern people
understand reproduction, many remain confused about what specifically causes
some common illnesses. If asked to define a bug, they may respond by saying it
is a germ. However, this answer only leads to three other questions.

First,
what is a germ? It is more accurate to refer to germs rather than germ, for a
germ is not one organism. In fact, germs exist in several microscopic forms. When people say they have
caught the flu bug, they are actually referring to a virus, one of the four
forms of germs. Viruses are microorganisms that must live inside living cells
in order to grow and reproduce. Outside their hosts, they will die. Tiny, one-cell
germs, called bacteria, also need hosts in order to live. Sometimes, these
hosts are humans; other times, they are not. Another group of germs, called
fungi, also needs plants or animals in order to live. This is because fungi
cannot manufacture their own food. However, unlike the other two groups, they
do not usually live inside people. The last group of germs is protozoa, the
smallest known members of the animal kingdom. Protozoa live in soil. In order
to live, they receive nourishment from dead or decaying organic material. They
are often found in rivers and other sources of water because they prefer a moist
environment. If people ingest this contaminated water,
the protozoa will enter their bodies, where they will reproduce and grow.

If
germs depend on humans and other organisms for their reproduction and growth,
are germs harmful? The answer to this question is both yes and no. Some
examples using bacteria will help explain this answer. If a bacterium such as Streptococcus
pneumoniae enters the human body, pneumonia – an
infection that can lead to death – may occur. However, without bacteria, humans
could not live, for many bacteria are also good for people’s bodies. Bacteria
live in the intestine, where they help the body use the nutrients in food. In
addition, they help turn excess nutrients into waste that is later eliminated
from the body.

How
are germs spread? They are transmitted
in a variety of ways. A major source of transmission is the air. When people
have a cold, they often sneeze. If they do not cover their mouths when they
cough, germs enter the air and spread. Humans are also another source of
transmission. Soap and water destroy most germs, so unclean hands can spread
these organisms to other people. However, humans are not the only means of
transmitting germs. Insects can be a source of transmission. For example, if a
tick infected with Borreliaburgdorferi bites people, they can develop Lyme disease.

To
summarize, germs are microscopic organisms – especially ones that cause
diseases – that can be described according to three major aspects. They exist
in four forms. While most people think of them as always being harmful, these
tiny organisms can be beneficial at times. They are transmitted in three major
ways.